Yeah, you do run into a number of fake masters, when you're trawling different s/m forums, the guys who will write to you as soon as you've made a few posts and indicated you're a masochist, and introduce themselves as "very experienced and strict master", start calling you slave instantly etc.
On another forum I got in touch with this guy who sent me a questionnaire of my tastes, limits and wishes - bet he did that for all the people he contacted - and within a week he was asking me to rig my webcam (I didn't have one at the time, recently got one and am learning to use it) so he could order me around for hours.. I was more into exchanging fantasies and roleplay, but he went for the kill and when there was a two-day break in the mail exchange he sent me a mail. asked for explanations and then "sentenced" me to some outrageous punishments and then to write him a report of what it had felt like.

The next day I wrote a fake horny report on how the treatment had turned out and then pulled the plug on the poor man, I just felt "I don't have time for this kind of guy now". Haven't met any of that kind on this forum though, that's nice.